Nearly half a million Syrians have returned to their homes since the beginning of the year, mainly to find family members and check on property, the UN refugee agency said Friday.

The agency said it had seen "a notable trend of spontaneous returns to and within Syria in 2017" but cautioned that conditions were "not yet in place" to guarantee their future safety.

Andrej Mahecic, a spokesman for the UNHCR, said about 440,000 people forced to move to other areas of Syria by war had returned to their homes. They were mainly from Aleppo, Hama, Homs and Damascus.

UNHCR believes conditions for refugees to return in safety and dignity are not yet in place in Syria

- Andrej Mahecic, UN refugee agency

In addition, about 31,000 refugees in neighbouring countries had also returned, he said, bringing to 260,000 the number of refugees who have returned to the country since 2015.

But Mahecic said the figures were a mere "fraction" of the five million Syrian refugees hosted in the region.

He said the main factors prompting returns were "seeking out family members, checking on property, and, in some cases, a real or perceived improvement in security conditions in parts of the country".

He said it was too early to say if the returns could be directly linked to a drop in violence since a Russia-Turkey agreement in May to create four "safe zones" across Syria to ban military flights and ensure aid drops.

But this week, the UN's special envoy for Syria, Staffan de Mistura, told the Security Council that since the 4 May deal, "violence is clearly down. Hundreds of Syrian lives continue to be spared every week, and many towns have returned to some degree of normalcy."

Mahecic said: "While there is overall increased hope linked to the recent Astana and Geneva peace talks, UNHCR believes conditions for refugees to return in safety and dignity are not yet in place in Syria.

"There remain significant risks of protection thresholds for voluntary, safe and dignified returns not being met in parts of the country.

"Access to displaced population inside Syria remains a key challenge."

The agency had begun scaling up operations inside Syria to better address the needs of those who had returned, he said.

Syria's war has killed more than 320,000 people and forced millions from their homes since it began in March 2011.